Wednesday, February 5, 2014

Claim: Warming of 0.09°C over the past 55 years is 'slowly but steadily cooking the world’s oceans'

A news article published today claims "climate change is slowly but steadily cooking the world’s oceans," and that "some 378 million Hiroshima bombs worth of heat a year [allegedly from Mann-made global warming] are begging for our attention." Yet, for some reason, the article fails to mention that the world's oceans have only warmed a tiny nine-hundredths-of-one-degree [0.09°C] over the past 55 years, at a rate of about 2-one-thousandths-of-one-degree [0.0016°C] per year.

Because the ocean’s so big—it takes up more than 70% of the planet’s surface—it absorbs a lot of energy without anyone being much the wiser. Here’s a look at data for the upper 2,000 meters (1.14 miles) of the global ocean. Check out the three-month moving average for the last quarter of 2013, via the National Oceanographic Data Center, which actually goes off the chart:

​ National Oceanographic Data Center (NODC)

Roughly speaking, from about 1980 to 2000, the ocean gained around 50 zettajoules (ZJ, or 1021 joules) of heat. But from 2000 to 2013, it added another 150 ZJs of heat. Of course, even if you knew what a zettajoule is, it’s hard to envision what this means. Science Skeptic, a blog on climate change, offers this useful analogy: Over the last half-dozen or so decades, the ocean’s been storing the heat energy equivalent of about two Hiroshima bombs per second. Worryingly, that rate’s picking up, with around four bombs per second stored in the last 16 years.

In 2013, however, the ocean gained the heat equivalent to about 12 bombs per second, says Science Skeptic.

​”Thermosteric” means how much sea surface height changes due to temperature-induced expansion or contraction of ocean volume. National Oceanographic Data Center (NODC)

The variation in surface temperature is a big reason people suspect that the earth is getting warmer.

Deep-ocean temperatures are among the more consistent indicators of how our climate is changing. Solar energy transmitted by greenhouse gases doesn’t necessarily translate to warmer surface temperatures, which are also influenced by a slew of other factors, including wind and current. In the last decade, around one-third of global warming showed up 700 meters under the sea’s surface or deeper, according to research (pdf) by Magdalena A. Balmaseda, Kevin E. Trenberth and Erland Källén published last year.

So while it’s easy to ignore what’s going on a mile under the waves, some 378 million Hiroshima bombs worth of heat a year are begging for our attention.

Climate scientists claimed for decades that AGW would cause land temperatures to warm before ocean temperatures, but when land temperatures stopped rising, started to claim the exact opposite that ocean temperatures could rise first.

Ocean heat content 0-700 meters has plateaued since ~2004, when much higher quality data became available from the ARGO float system. Data shown after up-justed from cooling to warming trend by Josh Willis of NASA/JPL

I cringe every time I see the heat content of anything expressed in terms of 20 kiloton bombs. Such a metric does not even have the merit of "dumbing down".the physics so people can understand it.

Who knows the significance of an atom bomb? Why not just use megaCalories or gigaCalories? A Calorie is a physical unit the is in common use. You can read abut Calories on your cornflakes box.

The point that needs to be made in discussing the heat capacity of the oceans is that the top 3 meters (10 feet) of the ocean contains as much heat as the entire atmosphere right up to the top where it meets the vacuum of space.

There is no mystery about this and it's not controversial. I will demonstrate how simple some of these calculations are. Not rocket science by a long shot.

This calculation is based on two metrics that you can calculate easily.

Air pressure is about 14 pounds per square inch at sea level. (Your car tires needs about twice this pressure.)

Fourteen pounds per square inch is about 9.9 metric tons per square meter. Which tells us that the column of air weighs the same as a column of pure water 9.9 meters deep. [one cubic meter of pure water weighs one metric ton / 1000 kilograms.]

The density of sea water is about 3% more than fresh water. So the column of air over a square meter of sea water weighs about the same as 9.6 cubic meters, a column of seawater 31.5 feet deep.

So compared to water, how much heat would the air hold? Air has a heat capacity of 1005 J/kg/°K and seawater about 3993 J/kg/°K. So air by weight has about 25% of the heat capacity of seawater.

We do not have to know what "J/kg/°K" means because we only use the ratio or percentage. The result is that 25% of 9.6 meters of seawater or 2.4 meters (8 feet) holds the equivalent of the entire heat capacity of the column of atmosphere standing above it.

One last step. The oceans take up about 70% of the Earth's surface. So we adjust by dividing 2.4 meters by 0.7 and get 3.5 meters or 11.25 feet.

The oceans have about the same heat capacity in the top 3.5 meters (11.25 feet) as the entire atmosphere.

Satellite measurements give the average depth of the oceans as 3,682 meters. The oceans have about 100 times the heat capacity of the atmosphere.

Note: The value of heat capacity of the atmosphere shown here is close to the figure.obtained by Julia Cole in the panel entitled "Heat Capacity" in the PDF

She posted 3.2 meters probably using precise conversion figures while I do most of this from memory on an Excel spreadsheet.. High school stuff most of it and I left high school around 1950 or so.

http://www.geo.arizona.edu/geo4xx/geos412/OcSci07.PhysProps.pdf

As Richard Feynman liked to say, What is the meaning of it all?

Well the meaning is clear I think. During an interglacial cycle of 100,000 years or so the oceans act as a huge heat buffer, heat sink.

It would take a very long time for the atmosphere to heat the oceans to any significant depth, hundreds of years, perhaps 1000 years. But a very short time for the oceans either to warm the atmosphere or to cool the atmosphere probably decades.

This probably explains why the various ocean oscillations, ENSO, AMO, and PDO have short cycles of 10 to 60 years.

It probably also explains the 800-year lag in CO2 content of the atmosphere when the glaciers recede. The oceans take a long time to warm up when the glaciers melt and as the oceans warm they "outgas" CO2 for the same reason your Coca Cola outgases in a warm room.

If you are keen to study climate, begin with the oceans and then study the atmosphere.